YAKUTAT BAY GLACIERS 37 positions of the larger glaciers by the construction of plane table maps by Mr. Henry Gannett. Maps of similar character were also made by the United States Geological Survey expeditions of 1905 and 1906 by Messrs. Butler (in 1905) and Rich (in 1906). It was part of the plan of the National Geographic Society's expeditions of 1909-10 to make more detailed maps of the larger glaciers of Yakutat Bay as a basis for future studies of the changes in these glaciers, and for this purpose one of the topographers of the United States Geological Survey, Mr. W. B. Lewis, was attached to the expeditions. Assisted by E. F. Bean and F. E. Williams, he has made the contour maps which accompany this book. All future students of the glaciers of this region will find in their carefully-made maps a reliable basis for comparison of the positions of the glacier fronts as they may change from time to time. Recent Advance of the Glaciers. Earlier in this chapter it has been intimated, and in other publications stated with full delkil,1 that some of the glaciers in the Yakutat Bay region have been recently subjected to an advance of such unusual character as to lead to the desire to study the phenomenon further. It was primarily this desire that led us to return to the Yakutat Bay region in 1909 and 1910, and the results of the work of these years that are of most value relate to the phenomena attending the advance of the glaciers. These results will be stated in detail in later chapters devoted to the discussion of individual glaciers; but in order that these details may appear in their proper setting it seems desirable to make a general statement concerning the phenomenon. In 1905, while a general condition of recession characterized the great majority of the Yakutat Bay glaciers one, Galiano Glacier, presented convincing evidence of change to activity in the interval since it was photographed by Russell in 1890. Then it had a stagnant piedmont bulb on whose ablation moraine a forest of alder and cottonwood grew, proved both by Russell's description and by his photographs and also shown by Boundary Survey photographs in 1895. This forest growth had entirely disappeared in 1905, but the piedmont bulb was again stagnant and covered by ablation moraine, though with only young alders scattered here and there. Neighboring glaciers, for instance Atrevida to the west and Black Glacier to the east, gave no evidence of similar change, and no such evidence was found in any other glaciers. Puzzled by the phenomena, and forced to the hypothesis that it was in some way connected with the earthquakes of 1899, we made no attempt at explanation but merely described the facts. We were not at all prepared for the momentous changes which occurred in the interval between the summers of 1905 and 1906. Returning to Yakutat Bay in 1906, the senior author found four glaciers absolutely transformed, and all the others unchanged. These glaciers that were so altered in the brief interval of nine or ten months are, named from west to east, the Marvine Glacier and the eastern lobe of the Malaspina Glacier that is fed by the Marvine, the Atrevida Glacier, Haenke Glacier, and Variegated Glacier. In the summer of 1905 one could travel over the surfaces of these glaciers at will. On two of them, Atrevida and Variegated Glaciers, we walked freely, on the former late in August, without recognizing any signs of coming change to activity. The glaciers were crevassed slightly only here and there, and outside the mountain were in a stagnant or semi-stagnant condition and covered with a waste of ablation moraine; but in June, 1906, all four glaciers were trans- i See especially, Tarr, R. S., The Yakutat Bay Region, Akska, Professional Paper 64. U. S. Geol. Survey, 1009, pp. 41-95, Here -will be found references to other publications on the subject.